1. Field of the Invention
This invention relates to nucleators for generating magnetic domains, and more particularly to a magnetic bubble domain generator which can be integrated into circuitry used to perform other functions with the magnetic bubble domains.
2. Description of the Prior Art
Many devices have been proposed in the prior art for generating magnetic bubble domains in a magnetic bubble domain material. These devices can be divided into two classes: those which generate bubble domains by replication from an existing bubble domain, and those which initially nucleate a bubble domain in the magnetic bubble material. Although many designs have been proposed for bubble domain replicator generators, such bubble generators have limitations when used at high frequencies. Therefore, bubble domain nucleators have been thought to be more preferable as the operating frequency of bubble devices has increased.
U.S. Pat. No. 3,662,359 describes a bubble domain nucleator which comprises a magnetic element for creating a localized magnetic field as well as a current carrying loop for creation of the localized magnetic field. Additionally, U.S. Pat. No. 3,706,081 describes a bubble domain nucleator in which permalloy is adjacent to the magnetic bubble material in order to produce a more intense magnetic field for nucleation of bubbles. In this latter reference, an opening is created in the insulating layer located over the bubble domain material in order to have the permalloy elements be closer to the bubble domain material.
In order to have stable bubble domain devices using bubble domains of two microns diameter or less, current carrying bubble domain nucleators become impractical due to a high current density requirement for nucleation. That is, for smaller bubble sizes, the anisotrophy of the bubble material has to be large and this in turn requires larger magnetic fields for nucleation of bubble domains in the bubble domain material. However, the need for larger magnetic fields means that larger currents will be required in the current carrying conductor of the bubble nucleator. As an example, it has been found that current carrying conductors would not nucleate two micron bubble domains in amorphous magnetic GdCoMo films at currents up to about 30 ma. This corresponds to a current density of approximately 10.sup.7 amps/cm.sup.2. The need for large currents in the current carrying conductors comprising the bubble domain nucleators leads to electromigration problems.
The present invention seeks to provide bubble domain nucleators comprising current carrying conductors which do not suffer the problems of adverse effects due to electromigration when very small magnetic bubbles are to be nucleated. Accordingly, it has been discovered that when the nucleating current passes through the amorphous magnetic medium the current required for bubble domain nucleation is significantly less than would be if there were no current passage through the amorphous bubble medium.
Accordingly, it is a primary object of this invention to provide improved magnetic bubble domain nucleators comprised of current carrying conductors.
It is another object of this invention to provide nucleators for nucleating magnetic bubble domains in amorphous magnetic materials which are not hampered by adverse effects of electromigration.
It is another object of this invention to provide an improved bubble domain nucleator using current carrying conductors which utilizes the magnetic bubble material as a current conducting medium.
It is another object of the present invention to provide an improved bubble domain nucleator for nucleating very small bubble domains in amorphous magnetic media.